This invention relates to penetrable doors or closures formed of a plurality of vertically hanging and laterally overlapping, preferably transparent, flexible strips of the type which are in common use today to cover openings such as door openings to provide an environmental barrier. Such door assemblies are useful to reduce heat or cold loss, to restrict the movement of air pollutants and even flying insects, and to isolate noisy machinery. They are used to provide temperature-controlled barriers between rooms, to cover openings for overhead craneways, to function as secondary doors on receiving and loading docks, as telephone enclosures, in car wash installations, as conveyor assembly line opening covers, and as storage area enclosures. Many diverse constructions have been proposed and are in use and among them are the constructions utilized in the following patents:
______________________________________ 4,033,396 Thomasset 4,289,190 Catan 4,086,950 Power 4,340,106 Van Horn, II 4,095,642 McKinnon et al 4,384,606 Johnston et al 4,165,778 Smith 4,388,961 Schaefer et al 4,257,471 Thurmond ______________________________________
While providing a thermal barrier, and a closure which restricts the movement of air pollutants such as dirt, smoke, fumes, dust, drafts, and the like, a door of this type must be readily penetrable by a vehicle, person or product. In recent years, considerable attention has been directed to providing a construction which can be readily afforded by those parties or businesses which must utilize a closure of this character, and there is a real need for such a system.